1. Field of the Invention
The present invention relates generally to a light illuminating type switch and, more particularly, to a switch illuminating light by an electroluminescent sheet.
2. Description of the Related Art
A conventional light illuminating type switch in which an electroluminescent sheet of a type not integrated to a movable contact is provided on the movable contact electrically connected to a fixed contact provided on a switch sheet by being elastically deformed to thereby illuminate the switch is described in Japanese Patent Laid-Open No. 144172, published in 1998.
When an electroluminescent sheet is not used as a light source for illuminating light, as shown in FIG. 15, a light emitting diode (LED) 102 is arranged above a switch sheet 101, and illuminated light from LED 102 is diverged via a key operating pad 103 to thereby illuminate the entire switch.
According to the conventional light illuminating type switch for illuminating light by the electroluminescent sheet by using the movable contact, the electroluminescent sheet and the movable contact are not integrated with each other and, therefore, unitization of the light illuminating type switch is incomplete. That is, the light illuminating type switch is constituted merely by providing the electroluminescent sheet above a conventional switch. Therefore, also in view of integration steps, later steps undergo load of integration.
Further, according to the light illuminating type switch using an LED, the LED per se constitutes a point light source and, accordingly, the entire surface of the switch cannot easily be uniformly illuminated. The entire surface of the switch can be uniformly illuminated by using a key operating pad made of a material comprising, for example, silicone rubber dispersed with white pigment. The key operating pad diverges the light illuminated by the LED. However, in this case, a satisfactory result cannot be attained in uniformly illuminating the entire surface of the switch by using a key operating pad having a thin thickness. In practice, a key operating pad having a thickness of 2.5 through 3.0 mm is used, which hampers formation of a thin light illuminating type switch.
There is, therefore, a need in the art for a light illuminating type switch with a thin construction that is suitable for use in thin and light-weight apparatus, such as a portable telephone or a personal digital assistant. There is further a need in the art for such a switch to possess excellent clicking performance in ON/OFF operation of the switch.
The present invention is directed to an apparatus that satisfies the need for a light illuminating type switch that has a thin construction and that possesses excellent clicking performance in ON/OFF operation of the switch.
According to the embodiments of the present invention, a movable contact and an electroluminescent sheet are constructed in an integrated and thin structure by attachedly pasting together the movable contact and the electroluminescent sheet to thereby enable to supply a light illuminating type switch at the stage. Further, a method of adhering the electroluminescent sheet to the movable contact to conform the electroluminescent sheet to the shape of the movable contact provides a switch having excellent click feeling.
According to an embodiment of the present invention, a light illuminating type switch comprises: fixed contacts provided on a switch sheet; a movable contact capable of electrically connecting to the switch sheet by being deformed elastically arranged above the switch sheet; and a flexible electroluminescent sheet is attachedly pasted on a surface of the movable contact by interposing an insulating member as far as a peripheral portion thereof other than the movable contact.
In a preferred embodiment, the electroluminescent sheet and the movable contact may be attachedly pasted together by an adhesive material interposed between the electroluminescent sheet and the surface of the movable contact. The adhesive material may be interposed between the electroluminescent sheet and only a portion of the surface of the movable contact to thereby attachedly paste together the electroluminescent sheet and the movable contact.
In a further preferred embodiment, the electroluminescent sheet and the movable contact may be attachedly pasted together by a sheet with a double-sided adhesive material interposed between the electroluminescent sheet and the surface of the movable contact. The sheet with the double-sided adhesive material may be interposed between the electroluminescent sheet and only a portion of the surface of the movable contact to thereby attachedly paste together the electroluminescent sheet and the movable contact.
In a preferred embodiment, the movable contact may be a metal member formed in a dome shape. The metal member formed in the dome shape may be formed in a net-like shape.
In a further preferred embodiment, the electroluminescent sheet and the movable contact may be attachedly pasted together by the adhesive material or the sheet with the double-sided adhesive material interposed between the electroluminescent sheet and the surface of the movable contact, and the adhesive material or the sheet with the double-sided adhesive material may be interposed between the electroluminescent sheet and approximately 80% or less of an arc-like portion of the surface of the movable contact.
The electroluminescent sheet may be pre-molded or plastically deformed to constitute a shape that conforms to the shape of the movable contact. The electroluminescent sheet may be formed by successively laminating a transparent electrode layer, a luminescent layer, an insulating layer, and a rear electrode layer on a flexible transparent film, and at least one layer of the luminescent layer, the insulating layer and the rear electrode layer may be omitted at a portion of the electroluminescent sheet disposed above a surface portion of the movable contact.
In a preferred embodiment, a key operating pad is arranged above the electroluminescent sheet. In a further preferred embodiment, the key operating pad is formed in a sheet-like shape.
The above, and other features, aspects, and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.